The background description provided here is for the purpose of generally presenting the context of the disclosure. Work of the presently named inventors, to the extent it is described in this background section, as well as aspects of the description that may not otherwise qualify as prior art at the time of filing, are neither expressly nor impliedly admitted as prior art against the present disclosure.
Hybrid vehicles typically use a powertrain system including an engine, a stop-start or mild hybrid system including a starter/generator and/or one or more electric motors for propelling the vehicle. During operation, current needs to be supplied to start the engine, to supply loads connected to a vehicle power bus, to restart the engine, to drive the electric motors or starter generator to move the vehicle and/or to recharge the batteries. For example in some mild hybrids, the electric motors or starter generator drive the vehicle for brief periods such as 1-2 seconds during restarts to eliminate engine hesitation as the engine cranks, starts and reaches idle or other engine speed (hereinafter referred to as e-boost). As a result, significant engineering effort has been invested to improve the battery systems of hybrid vehicles to meet the increasing current loads.
The automotive industry has also proposed using batteries operating at higher voltage levels such as 24V, 36V and 48V and/or systems incorporating supercapacitors or ultracapacitors. However, these systems are fairly complex since they still need to operate with legacy 12V vehicle systems and components.
Some vehicle battery systems include a 12V battery in addition to a higher voltage battery, a supercapacitor or an ultracapacitor. However, these systems require a full capacity 12V battery, such as 100 Ah, in addition to the higher voltage battery, supercapacitor or ultracapacitor.